JPH0796414B2 - Paper skew detector - Google Patents

Description

The present invention relates to a skew detection device for a sheet that detects skew.

[Prior Art] In a recording apparatus or the like that feeds paper by a platen roller, paper skew occurs due to various causes. The sheet skew means that when the paper feed direction is the X axis, the amounts of movement of both sides of the paper that should be kept substantially parallel to the X axis are different from each other, and the X axis and the Y axis (Y
The axis is perpendicular to the X-axis) and the directions are X-axis and Y-axis on the paper.
This is a phenomenon in which the axes do not match, and if a paper skew occurs, the recording result becomes inaccurate, so it is necessary to promptly detect the skew and correct it by some method.

FIG. 2 is a perspective view showing an example of a conventional paper skew detecting device. In the figure, (1) is paper, (2) and (3) are sensors, and (4) is printing on both sides of paper (1). It is the scale that was set. The scales (4) are printed at equal intervals on both sides (hereinafter, referred to as left and right sides) parallel to the X-axis which is the paper feeding direction, and the positions of the left and right scales (4) on the X-axis match. . The sensors (2) and (3) are, for example, sensors that generate one pulse each time one scale is detected. Therefore, the sensors (2), (3)
When the output pulses of 1 are counted by the counters 1 and 2 (not shown), the count values of the counters 1 and 2 represent the paper feed amount of each side, and the difference between them represents the skew amount.

FIG. 3 is a perspective view showing another example of the conventional apparatus, the same reference numerals as those in FIG. 2 denote the same or corresponding portions, and (13) is a cut end of the paper (1). When cutting the paper (1), use the cutter attached to the recording device to
Since it cuts parallel to the axial direction, this cut end (1
Check whether the direction of 3) matches the Y-axis direction on the paper (1) (direction perpendicular to the left and right sides of the paper), the sensor (2),
It is detected in (3).

[Problems to be Solved by the Invention] Since the conventional sheet skew detecting device as described above is configured as described above, it is necessary to print the scale in advance in the conventional device shown in FIG. And, after the recording is finished, unnecessary scales remain.

Further, the conventional device shown in FIG. 3 has a problem that it is difficult to accurately measure the cut end of the paper.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide a sheet skew detecting apparatus capable of accurately detecting the skew of a sheet without printing a scale on the sheet or cutting the sheet accurately. Has an aim.

[Means for Solving the Problems] A sheet skew detecting device according to the present invention is a patent application “Paper standard position control device for multicolor recording device and control method therefor” filed by the same applicant as the present applicant. Wish 1
-190302, The method started on July 21, 1991 (hereinafter referred to as the prior application) is used, and in the prior application, the physical quantity (for example, the intensity of reflected light) related to one side of the paper is measured in the X direction. Is measured as a function of the position of the paper, and a plurality of reciprocating motions of the paper in the X direction are performed a plurality of times, and the positional deviation of the paper in the X-axis direction is determined from the cross-correlation between the plurality of measured values. However, in the present invention, sensors are provided on both sides of the paper to measure the physical quantities on the respective sides, determine the misalignment of each side, and determine the skew amount of the paper from the difference in the misalignment of both sides. And

[Operation] If the distance between the two sensors provided on both sides is D, the skew amount of the sheet can be determined from the difference between the positional deviations on both sides and the value of the distance D.

Embodiments Embodiments of the present invention will be described below with reference to the drawings. First
1 is a perspective view showing an embodiment of the present invention, in which the same reference numerals as those in FIG.
(3) is a sensor similar to the sensor used in the previous application, and measures the physical quantity on each side (in other words, the intensity of reflected light). (5) is a platen roller.

For multi-color recording and the like, the paper (1) is fed after each color recording, and then rewound to record the next color. However, when the paper (1) is rewound, the paper (1 Regarding the function of the output of the sensor (2) with respect to the X-axis so that the origin on the X-axis in 1) exactly matches the origin in the previous recording,
The deviation of the origin between the previous measurement and the current measurement was determined from the cross-correlation between the previous measurement and the current measurement.

In the prior application, the sensor (2) is provided only on one side of the sheet (1) and only the deviation of the origin on the side is measured. However, when skew occurs, the deviation of the origin on one side is different from that on the other side. It does not match the deviation of the origin of the side.

According to the present invention, the deviation of the origin on both sides is separately measured by the respective sensors (2) and (3). Then, the skew amount is calculated from the difference between the deviations of the origins on both sides and the distance D between the sensors (2) and (3).

The skew amount can be corrected by electrically converting the position coordinates of the drawing when the paper (1) is skewed into position coordinates relating to the recording device and recording, or by mechanically correcting the skew itself of the paper (1). However, since this correction is not directly related to the present invention, its detailed description is omitted.

[Effect of the Invention] As described above, the present invention has an effect that the skew of the paper can be accurately detected without the need to print the scale on the paper or cut the paper accurately.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, and FIGS. 2 and 3 are perspective views showing a conventional device. 1 ... Paper, 2, 3 ... Image sensor, 5 ...
Platen roller. In the drawings, the same reference numerals indicate the same or corresponding parts.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location B41J 29/48 E (72) Inventor Koji Shimizu 3-19-6 Nishishinagawa, Shinagawa-ku, Tokyo Graph table (56) References JP-A-60-114988 (JP, A) JP-A-4-27570 (JP, A)

Claims (1)

[Claims] 1. When a sheet having both sides parallel to the X-axis is fed in the X-axis direction and a reciprocating motion of the sheet is performed a plurality of times in the X-axis direction, a skew of the sheet is detected. In the skew detection device, each sensor provided on each of the both sides to measure a physical quantity related to the side as a function of the position in the X-axis direction, and performs a plurality of measurements by the above sensors for the plurality of reciprocating motions. Then, means for determining the displacement of the side in the X-axis direction from the cross-correlation of the measured values of the function of the position of the physical quantity in the X-axis direction on each side, and the displacement of one side of the both sides. A skew detection device for a sheet, comprising: means for determining the skew amount of the sheet based on the positional deviation of the other side.